first many thanks to your reply.
see bellow.
On 1/25/07, Nathan Scott <nscott@xxxxxxxxxx> wrote:

Hi Raz,
On Wed, 2007-01-24 at 08:34 +0200, Raz Ben-Jehuda(caro) wrote:
> David Hello.
> I have looked up in LKML and hopefully you are the one to ask in
> regard to xfs file system in Linux.

OOC, which one? (would be nice to put an entry for your company
on the http://oss.sgi.com/projects/xfs/users.html page).
> These servers demand high throughput from the storage.
> We applied XFS file system on our machines.
>
> A video server reads a file in a sequential manner. So, if a
Do you write the file sequentially? Buffered or direct writes?

> file extent size is not a factor of the stripe unit size a sequential
> read over a raid would break into several small pieces which
> is undesirable for performance.
>
> I have been examining the bitmap of a file over Linux raid5.
I've found that, in combination with Jens Axboe's blktrace toolkit
to be very useful - if you have a sufficiently recent kernel, I'd
highly recommend you check out blktrace, it should help you alot.
(bmap == block map, theres no bitmap involved)
> According to the documentation XFS tries to align a file on
> stripe unit size.
>
> What I have done is to fix the bitmap allocation method during
> the writing to be aligned by the stripe unit size.
Thats not quite what the patch does, FWIW - it does two things:
- forces allocations to be stripe unit sized (not aligned)

I debugged xfs_iomap_write_delay:
ip->i_d.di_extsize is zero and prealloc is zero. is it correct ?
isn't it suppose stripe unit size in pages ?
Also , xfs_iomap_eof_align_last_fsb has this line :
if (io->io_flags & XFS_IOCORE_RT)
;

Provided you are writing sequentially, you should
be seeing xfs_iomap_eof_want_preallocate return true, then later doing
stripe unit alignment in xfs_iomap_eof_align_last_fsb (because prealloc
got set earlier) ... can you trace your requests through the routines
you've modified and find why this is _not_ happening?
cheers.
--
Nathan